Control system for gas-burning appliances



Sept. 24, 1957 A. L. MILLER 2,807,420

CONTROL SYSTEM FOR GAS-BURNING APPLIANCES 4 Sheets-Sheet 1 Filed May 4, 1951 IN VEN TOR. 4w L M. I. an

p 24, 1957 A. L. MILLER 2,807,420

CONTROL SYSTEM FOR GAS-BURNING APPLIANCES Filed May 4, 1951 4 Sheets-Sheet 2 all INVENTOR. 4w 1.. Mum

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CONTROL SYSTEM FOR GAS-BURNING APPLIANCES Filed Bay 4. 1951 4 Sheets-Sheet I5 IN VEN TOR.

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CONTROL SYSTEM FOR GAS-BURNING APPLIANCES Filed May 4, 1951 4 Sheets-Sheet 4 INVENmR.

' flyrl. Alli-LE? United States Patent CONTROL SYSTEM FOR GAS-BURNING APPLIANCES Avy L. Miller, North Hollywood, Calif.

Application May 4, 1951, Serial No. 224,497

7 Claims. (Cl. 236-9) My invention relates generally to gas-burning appliances, and more particularly, to a system for controlling the delivery of fuel gas to the main burner in such appliances, and to safety features incorporated in the system.

Fuel gas-burning appliances, for purposes of heating water, for space heating, and for similar household and industrial applications, are well known, and fall generally into two classes, to wit, (1) those systems in which the demand-responsive control of the appliance is accomplished by turning the main burner full on when heat is required and turning it off when a predetermined temperature is reached, and (2) systems in which the supply of fuel gas to the main burner is modulated in accordance with the heat requirements.

Both of the systems above described have certain advantages and disadvantages in certain applications, and it is one of the purposes of the present invention to combine the advantages of both systems in a single control assembly.

One of the principal disadvantages of the on-01f regulation system is that there is no circulation of air during the o periods, and as a consequence, stratification of air occurs, the floor areas becoming cold and the ceiling areas hot. This condition is aggravated in installations where the heater must be of large B. t. u. capacity to meet occasional peak demands, but where the average demands are considerably below such peaks.

The just described disadvantage of the "on-01f system is, to a large extent, overcome by the use of the continuous modulation system which operates quite successfully until the demand becomes relatively low. Under such low demand conditions, the burner is apt to be operated at considerably below what is called the safe burning rate." A burner operating at below the safe burning rate is easily blown out by sudden drafts or in some cases, the flame may flash back and burn in the plenum chamber instead of at the burner jets. Also, burning at below the same burning rate is likely to produce incomplete combustion and as a consequence noxious fumes which are particularly dangerous in unvented burners.

The same flash back may occur in on-off control systems if the action of the valve is not relatively quick in turning on the gas.

One of the most efficient, simple, and fool-proof methods of operating the main control valve of a fuel gas burner is by means of a relay valve system employing the main pressure of the gas as a power source for operating the valve. In the interests of simplicity, it is also desirable that the main valve be subject to control by two elements, to wit, (1) a demand-responsive thermostat, and (2) a pilot safety thermostat which shuts off the main supply in the event of failure of the pilot burner. While it is possible to accomplish such control by the use of two separate main valves connected in series, one of which is controlled by the demand-responsive thermostat and the other of which is controlled by a temperatureresponsive element associated with the pilot burner, it is highly desirable to incorporate both functions in the same 2,807,420 Patented Sept. 24, 1957 valve. When this is done, however, the further necessity arises of making the control of the pilot-responsive element paramount, e. g., if the pilot burner blows out while the main burner gas is off, and thereafter the demandresponsive thermostat operates in a direction to open the main burner supply, the latter operation must be blocked by the pilot-responsive control element, otherwise the main gas supply would be turned on but the gas would not be ignited due to the fact that the pilot is inoperative.

Bearing in mind the foregoing discussion and the disadvantages of conventional systems available heretofore, it is a major object of the present invention to provide a unitary control and safety valve assembly for gas burning appliances, and a system for the control of such an assembly whereby the same is under the paramount control of a pilot-responsive safety element, and under the secondary control of a demand-responsive thermostatic element.

Another object of the invention is to provide a valve of the class described which is controlled to modulate the main gas supply over a predetermined portion of the range down to a point of minimum safe burning rate for the main burner, and is thereafter operated in on-ofi" fashion for heat demands less than that provided by continuous operation at the minimum safe burning rate.

A further object is to provide an on-oil valve of the type just described which has an improved quick action.

Still another object of the invention is to provide a main supply control valve of the class described which is adaptable for control by either of two types of thermostats, one which is directly incorporated in the structure of the valve, and the other of which may be located remotely therefrom.

It is a further object of the invention to provide means in a valve of the class described for supplying gas for controlling the system during initial lighting of the pilot burner, such means being operative to interrupt the flow of gas to the main supply burner until the pilot burner is in operation.

A still further object is to provide a valve of the class described in which the gas employed to operate the main control valve is bled off into the pilot burner whereby to be safely consumed without creating an asphyxiation, combustion, or explosion hazard.

Briefly, the embodiments of the invention described herein for purposes of illustration constitute systems for controlling a gas burning space heater. In one form of the invention, a demand-responsive control thermostat is physically incorporated in the main control valve structure, and in another form, the control thermostat is remotely located and is connected to the main supply modulating and control valve by means of a capillary tube.

In each case, the supply control valve is diaphragmactuated for on-ofi operation, that is, the main valve is closed by admitting gas from the supply line into an enclosure or actuating chamber behind an actuating diaphragm, and is opened by releasing the gas from the actuating chamber. For demand-responsive operation, the admission and release of gas from the actuating chamber is controlled by a small, two-position relay valve which in turn is actuated by a thermo-responsive element. Additional safety means are provided for closing the main valve in the event of pilot failure. This last-named safety means comprises an assembly of three-way safety valves operated in response to a thermo-responsive element associated with the pilot burner, and adapted to shut off the gas normally flowing to the pilot burner upon failure thereof, and to deliver such gas instead to the actuating chamber to close the main supply valve. When the pilot gas is diverted in this manner, it is delivered to the actuating chamber through a passage that is otherwise used to bleed oil the actuating gas from the actuating chamber.

3 Thus, as will hereinafter be described in greater detail, the main valve will be held closed for so long a period as the pilot flame remains extinguished, regardless of the operation or condition of the demand thermostat.

In one of the forms of the invention, modulation control of the main valve is accomplished by applying an actuating force thereto, independent of the forces impressed by the diaphragm. Such independent forces are applied over a predetermined relatively high rate range of valve openings by means of a thermo-responsive element, such for example, as an expanding bellows. When thevalve is closed to a point of minimum safe burning rate, the temperature-responsive actuator engages th aforesaid relay valve to admit gas into the actuating chamber and close the main valve with a snap action. Provision is made for adjusting the point at which such snap action takes place so that the on-oil" operation is effected only over the range of heat demands which are lcss than the minimum safe burning rate.

The foregoing and additional objects. and advantages of the invention will be apparent from the following detailed description thereof, consideration being given likewise to the attached drawings, in which:

Figure 1 is an enlarged, elevational, partially sectioned view of a preferred embodiment of the main control valve and the pilot burner connected thereto;

Figure 2 is a horizontal section taken on the line 2-.--2 in Figure 1;

Figure 3 is a horizontal section taken on the line 3-3 in Figure 1;

Figure 4 is, an elevational section taken on the line 4-4 in Figure 3;

Figure 5 is an enlarged portion of the section in Figure 1, illustrating the operation of the relay valve, the same. being shown in on position;

Figure 6 is a view similar to Figure 5, but with the relay valve shown in an off position;

Figure 7 is a horizontal section taken on the line 7--7 in Figure 1;

Figure 8 is a plan view of a detent spring employed in the construction shown in Figure 7;

Figure 9 is an elevational section taken on the line 99 in Figure 7;

Figure 10 is an enlarged elevational section of a pilot safety valve assembly incorporated in the system shown in Figure 1;

Figure 11 i an elevational section taken on the line 11-11 in Figure 10;

Figure 12 is an elevational section taken on the line l2 l 2 in Figure 11;

Figure 13 is a horizontal section taken on the line 137-13 in Figure 12;

Figure 14 is an elevational view of a modified form of the invention incorporating portions of the system illustrated in Figure 1 adapted for remote control;

Figure 15 is a perspective view of a remote control unit employed in the system illustrated in Figure 14;

Figure 16 is a bottom plan view of the remote control unit illustrated in Figure 15;

Figure 17 is an enlarged elevational section taken on the line 1'7-17 in Figure 16; and

Figure 18 is a portion of the device shown in- Figure 17 taken on the line l818 in Figure 16, showing the control unit in an alternate operational position.

In the drawings, I have identified the main control valve assembly by the reference character 20, the valve being connected between the fuel gas supply main 21 and a burner supply pipe 22 leading to a main heating burner 23. Mounted adjacent the main burner 23 is a pilot burner assembly 24 which includes an elongated multiple jet pilot burner 25, a therrno-expansive control rod 26 mounted above the burner 25, and a safety valve assembly 27, controlling the supply of gas to the pilot burner 25 and operatively connected to the control rod 26. Primary air for the pilot burner is supplied through a conduit 28, and gas for the pilot is delivered from the main valve assembly 20 to the safety valve assembly 27 by means of a small tube or conduit 29. The main control valve assembly 20 and the safety valve assembly 27 are also interconnected by a bleed conduit 30, the purposes of which will be described in more detail hereinafter.

For a detailed description of the presently preferred form of the main control valve assembly 20, reference should be had to Figures 1 through 9. There it will be seen that the assembly comprises upper and lower body portions 35 and 36, respectively, which are clamped together by means of a plurality of bolts 37 threaded into the lower body portion 36.

The valve assembly 20 is adapted for both manual and demand-responsive control, the manual control element being mounted in the lower body section 36, while the demand-responsive control elements are carried. in the upper section 35.

A hollow conical valve plug 40 is mounted for rotation in the lower body section 36, and is formed with a peripheral port 41 which may be rotated to align with the burner pipe 22 whereby to permit gas to flow out of the interior of the conical plug to the burner 23. As can be seen best in Figure 4, the lower body section 36 is formed with double walls whereby to permit gas entering from the supply main 21 to pass upwardly into an annular chamber 42 and thence over the top of a knife-edge seat 43 and downwardly into the interior of the conical plug 40, as shown by the arrow in Figure 4. An annular screen 44 is mounted in the chamber 42 to filter the gas supply as it flows through the assembly 20 whereby to prevent foreign matter, such as pipe scale and the like, from reaching and plugging the burners.

A circular diaphragm 45, of flexible material such as synthetic rubber, is peripherally clamped between the body sections 35 and 36, and is exposed on its lower surface to the annular chamber 42 and at its upper surface to an actuating chamber 46. The center of the diaphragm 45 is thickened, as shown at 47, whereby to form a whim member positioned and adapted to seat against the knife-edge seat 43 and prevent gas from passing through the assembly 20- to the burner pipe 22.

A circular weight 48, secured to the upper surface of the diaphragm 45, urges the same downwardly so that whenever the pressures in the chambers 42 and 46 are equalized, the valve portion 47 of the diaphragm 45 is urged downwardly against the seat 43. Furthermore, it will be seen that when the pressure in the chamber 46 is'equal to the main gas pressure and the valve member 47 is seated so that the area within the seat 43 is subjectedto substantially atmospheric pressure, an additional force equal to the area within the seat 43 times the eflective pressure. of the supply gas is exerted on the seat portion 43 to hold it closed.

On the other hand, when the pressure in the actuating chamber 46 is allowed to become substantially atmospheric, the excess pressure in the annular chamber 24 (being the pressure of the supply gas) lifts the valve portion 47 and permits gas to flow through the assembly 20, as aforesaid.

It will be noted that, at the time the valve starts to lift, the upward force is equal to the gas pressure times the. annular diaphragm area outside of the seat 43. The valve will lift when this upward force. just overcomes the weight 48. As soon as the valve opens slightly, however, and gas pressure backs up within the area'inside of the seat 43, the entire area of the diaphragm becomes effective, and the greater unbalance of forces results in the aforesaid snap action."

Thus, Ol'lrOfi operation of the control valve is: accomplished by admitting gas, under main pressure into the chamber 46, or releasing such gas therefrom. Such admission and release of gas is accomplished by means of a relay valve assembly 50 which is mounted in the upper body section 35. Operation of the relay valve assembly 50 is best seen from an examination of Figures and 6.

The relay valve assembly 50 is positioned in an olfaxis bore 51 which bore is supplied with gas under main pressure by a passageway 52 having adjoining portions formed in the upper and lower body sections, and communicating with the connection of the supply main 21, as indicated in phantom line in Figure 3. The lower end of the relay valve bore 51 is communicated with the safety valve assembly through a passageway 53, and the control conduit 30. The bore 51 is also communicated intermedaite its ends with the actuating chamber 46 by means of an oblique passageway 54. The passageways 52, 53 and 54 may conveniently be formed in the body sections by drilling intersecting bores therein. The upper end of the bore 51 is closed by a threaded cap 55 having a flexible sealing diaphragm 56 thereunder to provide an hermetic seal. a

A valving member 57 is supported in the bore 51 for axial movement thereon, and is retained in an upright position by a guide bushing 58 which is threaded into the bore 51. The valving member 57 has an upwardly extending stem 59 which is loosely received in the guide bushing 58 so as to permit free vertical movement of the valving member 57 and also to permit passage of gas around the stem 59 from the upper end of the bore 51 to the lower end thereof. A flange 60 is formed on the lower end of the valving member 57 and has secured thereto a pair of annular gaskets .61 and 62, which are adapted to make sealing engagement alternatively with a shoulder 63 at the bottom end of the bore 51, or the under side of the bushing 58 as the valving member 57 is moved downwardly or upwardly, respectively. The bushing 58 is adjusted to provide a very small movement of the valving member 57 which is normally urged upwardly by compression spring 64 anchored in the bottom of the bore 51. ported in a center aperture of the cap 55, and arranged to press downwardly on the upper end of the stem 57 through the flexible sealing diaphragm 56.

Thus, by pressing downwardly on the button 65, the valving member 57 may be moved downwardly against the urging of the spring 64 to separate the gasket 62 from the undersurface of the bushing 58, and (since the movement is very small) at substantially the same time, close the gasket 61 against the shoulder 63. It will be seen that the effect of such movement is to interrupt the communication between the passageways 5 3 and 54, and establish communication between the passageways 52 and 54.

The last-named condition is illustrated in Figure 6, wherein it will be seen that gas under main pressure in the passageway 52 is permitted to pass downwardly around the stem 59 and through the passageway 54 into the actuating chamber 46, thus closing the valving por tion 47 of the diaphragm 45 against the valve seat 43. On the other hand, when pressure is released from the button 65 to permit the spring 64 to urge the valving member 57 upwardly, the connection between the passageway 52 and the chamber 46 is interrupted, and at substantially the same time, the gas then in the chamber 46 under main pressure is permitted to escape through the passageways 5453 and the bleed conduit 30 to the pilot assembly 24 to be consumed in the pilot flame, as

Alternatively, the fluid may be enclosed in a system com- An actuating button 65 is loosely supprising a remotely located bulb connected to the bellows by a capillary tube. An externally threaded plunger 67 is mounted to the lower end of the bellows 65a and slidably supported in an alignment bearing 68 so as to transmit the downward force exerted by the bellows 65a to the weight 48 secured to the upper surface of the diaphragm 45. A flexible sealing diaphragm 69 is interposed between the plunger 67 and the weight 48 so as to prevent the escape of gas from the actuating chamber 46, and yet to permit free operation of the valve 47-43 by the bellows 650.

Thus, it will be seen that as the bellows 65a expands or contracts due to temperature variations, the valving member 47 is caused to respectively approach or recede from the valve seat 43, thus modulating the flow of gas through the assembly 20. Adjustment of the range of modulation thus effected, to correspond to that required, is accomplished by means of an anchor screw 70 threaded into the upper end of the spider 66 and abutting the upper end of the bellows 65a to form an anchor therefor. The screw 70 is locked by a conventional lock nut 71. Further manual adjustment of the modulation control is provided by the fact that the spider 66 is threaded into the upper end of the upper body section 35, as shown at 72, and may be rotated through substantially 360 to move the entire spider 66 upwardly or downwardly in accordance with the lead of the thread at 72. A stop boss 73 and a corresponding abutment 74 prevent rotation of the spider 66 through more than 360".

It will be remembered that, at the lower limit of the modulating range, it is desired that the relay valve 50 be actuated to close the main valve 4743. This is accomplished by means of an adjustable flange 75 which is threadedly mounted on the plunger 67 for axial adjustment with respect thereto. A plurality of compression springs 76 press upwardly on the flange 75 to frictionally prevent the same from rotating after it has been adjusted to a desired position with respect to the plunger 67. R0- tation of the flange 75 is accomplished by inserting a rod or other slender tool into one of a plurality of capstan holes 77, located in a ring adjacent the periphery of the flange 75.

Thus it will be seen that the flange 75 may be adjusted to a position on the plunger 67 such that it contacts the relay valve actuating button 65 when the plunger 67 reaches the lower end of its modulating range. Due to the relative position of the apertures 77 and the spider 66, it is possible to make adjustment of the flange 75 after the valve is entirely assembled, and installed in the system which it controls, and after it has been determined what the safe burning rate of the burner 23 is. Due to the pressure of the spring 76 against the undersurface of the flange 75, the same is locked against inadvertent rotation and therefore remains in whatever position of adjustment it is placed.

The manual controls for lighting the pilot are positioned in the lower body section 36 and comprise the rotatable conical valving member 40, a hand knob 80 keyed thereto, a detent flange 81 (shown separately in Figure 8), a complemental detent member 82, and a compression spring 83. As can be seen in Figure 8, the detent flange 81 is formed with a D-shaped aperture 84, and a shaft portion 85 of the conical plug 40 is flattened on one side, as indicated at 86 in Figure 7, to correspond to the aperture 84 whereby the flange 81 is carried in rotation by the plug 40.

The detent flange 81 is formed of a relatively thin, resilient metal, and is notched at a number of points around the periphery, as at 87, whereby engagement of the notches 87 with an extruded boss 88 formed in the detent member 82 serves to hold the plug 40 in any of three positions to which it may be rotated by means of the knob 80. The detent member 82 is urged into engagement with the flange 81 by the spring 83, the pressure of which also serves to seat the plug 40 firmly in its conical bearing in the valve body section 36.

Near the lower end of the conical plug 40 is formed a circumferential groove 90 extending part way around the'circumference of; the plug, and positioned to align with a pair of radial passageways 91 and 92, the former communicating with the connection of the main 21 and the latter communicating with a vertical well 93 formed in the body 96 and containing a cup-shaped strainer 94'which may be inserted from the bottom through an aperture closed'by a threaded plug 95. A compression spring 96 serves to hold the strainer 94 in its proper position in the well 93 Two fluid connections, and 98 lead-from the well 93 exteriorly of the strainer 94 so that gas passing through the well-9310, either of thefluid cqnnections 97 or 98 is cleaned by the strainer 94. The fluid connection 98 is connected through the conduit 29 to the pilot assembly 24 for controlled delivery to the pilot burner 25 in a manner hereinafter to be described, The purpose of the upper fluid, connection 97 involves a modified system employing the present invention, and will, be described later herein.

Whenever the aperture 41' is aligned with the burner connection 22,, the relative position of the groove 90 is,

such that it aligns with the passageways. 91 and 92 and intercommunicates the same, as shown in Figure 3, thus delivering gas to the pilot, assembly 24 aswell as to the main burner 23. When the, plug is rotated to the position shown in full line in Figure 1, i. e., that in which the aperture 41 is rotated substantially 90 baclt of the plane of the drawing, it will he noticed from an examination of Figure 3 that the groove 90 still aligns with, and intercommunicates the passageways 91 and 92 to deliver pilot gas, but that the main burner supply is shut off. Thus, when the pilot is to be, initially ignited, the plug 40. is rotated to theposition shown in Figure l, the pilot lighted and permitted to burn for a: long enough period to heat thethermo-responsive element 26, whereupon the knob, 80 is then rotated tobring the aperture 41. into alignment with the burner pipe 22 whereupon the automatic operation of the system may proceed as previously described. The plug 40. may also, be rotated to, a third position beyondthat shown in Figure 1. In the third position, the main burner supply is cut off by the nonalignment of the aperture 41 and the pilot supply is blocked by non-alignment of the groove 90.

Turning now to the discussion of the pilot valve assembly 27, reference should be-had to Figures through 13. As best seen in Figure 13, the pilot valve assembly 27 includes a solid body 100 having a number of bores and passageways formed therein. The automatic features of the pilot valve assembly are carried out by a pair of twoposition valves, positioned in a pair of transverse bores 101 and 102. Since the construction of the valves is identical, a description of one suflices for both.

The valying action is accomplished by movement of a ball 104 between alternate positionsseated against either a fixed seat 105 formed adjacent the inner end of the bore, or an adjustable seat 106 which is threaded into the bore. The movement of the ball 104 from one seat 105 to the other 106 is very slight, being on the order of a few thousandths of an inch. Such movement serves to communicate a vertical passagfiway 1030 in bore 101., 103b in 102, selectivel with either oftwo passageways adjacent opposite ends of the bore, such passageways being, in the case of the bore 101, an oblique downwardly leading passageway 113 located to the right of the ball 104 in Figure 10, or a transverse passageway 114. located to the left of the ball 104. The bore- 101. is communicated through, its vertical P lssageway' 103 with the pilot gas conduit 2% and thus when; the ball 104, is. seated against the seat 106, the valve space 104,105 is open. and pilot gas is delivered through the oblique passageway 113 to an adjustm nt chamber 120, hereinafter to be described.

The bore 102 is communicated. through its vertical passageway 103b with the conduit 30, and thus receives the actuating gas from above the diaphragm 45 when the latter is released. Thus, when the ball 104 in the bore 102 is against the seat 106 therein, such actuating gas is delivered through the diagonal passageway 115 into the air intake stream, as shown in Figure 12. Thus, such gas is drawni'ntothe pilot burner 25 and there consumed.

Normally; a compression spring 107. urges the ball 104 against the seat 105. Both of the balls 104 are liftedfrom the seats 105'and pressed against the seats 106, however, whenever the burner is ignited, and the thermoexpansion elements 26 heated. This operation is accomplished by a thrust transmitting bridge 116 connected intermediate its ends to the end of the thrust rod 26, and

adjacent its ends to a pair of thrust rods positioned to transmit the thrust of the rod 26 (when the latter is expanded) through intervening thrust balls 109 to the valve balls 1041 A flexible sealing diaphragm is interposed between each thrust rod 110 andthe corresponding thrust ball 109, and is held in place by a threaded plug 112 which also serves as a guide bearing for the thrust rod 110'. Provision for adjusting the operation of the thermo-expansion rod 26 is made in the form of a pair of nuts 117 and 118 which may be adjusted along the rod 26 onto which they are threaded, and mutually locked against each other. The outer end of the rod 26 is anchored by means of an upstanding abutment 119 welded to the outer end. Of the burner 25. The materials of the burner 25 and of theexpansion, rod 26 are so selected as to have substantially different coeflicients of expansion whereby the, rod 26, when heated by the burner 25, elongates to operate both of the balls 104.

Upon failure, of the pilot burner, the thermo-sensitive rod 26 contracts, releasing the holding pressure on the balls 104, and. permitting the springs 107 to urge both of the valve balls against the forward or inner seats 105. This. operation. of the valves, it will. be seen, closes both the passageway. 1.13 and. the passageway 115, thus terminating any further delivery of gas to the pilot burner and also closing off the communication of the actuatingchamber 46. from. atmospheric pressure (substantially), in the air intake passageway 28. The same movement of the valve balls.104. (to the right in Figure 13) opens the back valve spaces. 104-406, and intercommnnicates the two bores 101--102 through the transverse passageway 114. Thus'the pilot gas, previously delivered to the pilot burner through the conduit 29, is now delivered back through the bleed conduit 30 to the actuating chamber 46 whereby to hold the valve 47-43 closed and prevent further operation of the main burner 23 regardless of the then condition of the bellows 65a.

If the relay valve 50 should, at the time of pilot failure, be in its lowermost position so as to interrupt the bleed conduit 30, gas under main pressure will still be delivered into the actuating chamber 46, through the normal operation of the relay valve 50, the gas being delivered through the vertical passageway 52 as previously described.

It will be realized that, at the time the pilot burner 25 is first ignited, the thermo-sensitive control rod 26 will be contracted and thus the valve ball 104 in the bore 101 will be in a position to block flow of gas to the pilot burner. To provide for initial lighting of the pilot burner, a manual release lever is provided, and is positioned adjacent the thrust rod 11:0. aligned with the bore 101 so that inward movement of the lever 125 moves the ball 104 away from theseat 105 and against the seat 106 to permit temporary delivery of gas to the burner 25. The connection between the bridge 116 and each thrust rod 110 is made in the form of an aperture adjacent the end of the bridge which receives a reduced end portion of the rod 110 and permits independent movement thereof. The lever 125 is made of a resilient metal and is riveted to a cover 126 which is secured to the valve body 100, and provides dust protection for the valve operating mechamsm.

Control of the amount of pilot gas delivered to the burner 25- is accomplished by, conventional needle valve construction, including a threaded valve needle 121 operass-2,420

ated by a knob 122 and aligned with the conventional needlevalve seat 123 to regulate the amount of gas admitted through an orifice 124. A conically pointed screw 12'! is threaded into the body 100 and is positioned in the jet stream from the orifice 124 so as to cause turbulence in the latter and a more thorough mixing of the gas with the air drawn in through the intake 28. The jet from the orifice 124 acts in the usual Venturi manner to draw in air for mixture with the gas.

In the remote control modification of the system illustrated in Figure 14, the lower body section 36 and the parts therein are identical to those illustrated in Figure 1. In the modified version of Figure 14, however, the upper body section 35 is replaced with a cap 130 having mounted therein a compression spring 131 which is positioned to exert a downward force on the diaphragm 45. The actuating chamber in the modified form is within the recess in the cap 131, and is identified by the reference character 132. A fluid connection at 133 receives a conduit 134 which leads to a remote control unit 135, the latter being located at a point in the room which is most representative of the average temperature of the entire room so as to control the operation of the heater in accordance with the temperature at such control point.

Two additional control conduits 136 and 137 lead from the temperature control unit 135 to the pilot safety valve 27, and the main control valve assembly 20a, respectively. The control conduit 137 is connected to the assembly 20a at the upper fluid connection 97, and thus receives gas under main pressure whenever the valve plug 40 is set in position to provide gas for the pilot burner 25.

The temperature control unit 135 is constructed with a lower body section 140 having a central bore 141 therein with a small two-position valve member 142 supported therein similarly to the relay valve 50 in the main valve assembly 20. The operation of the valve member 142 is similar to that of the member 57 and has a similar flange and gasket thereon adapted to close either against a seat 143 at the bottom of the bore 14, or a movable seat 144 adjacent the upper end. Movement of the valve member 142 serves to communicate the fluid conduit 134 selectively either with the conduit 13'! or conduit 136, thus serving to either admit gas into the actuating chamber 132 or discharge the same to the pilot safety valve assembly 27 in the same manner described earlier in connection with the form illustrated in Figure l.

The upper end of the bore 141 is closed by means of a threaded cap 150, and a flexible sealing diaphragm 151 similarly to the previously described embodiment. An actuating button 152 is loosely held in a central aperture in the plug 150 whereby the valving member 142 may be actuated by downward thrust.

Operation of the valve member 142 in response to temperature changes is accomplished by a plurality of bimetallic dished discs of well-known design, which are centrally apertured and threaded onto an alignment rod 155, the upper end of the pile of discs 154 being anchored by an adjustment screw 156 carried in a spider 157 which in turn is threaded onto the body 140. When the temperature increases, the pile of discs 154 expands in the usual manner, and the thrust created thereby is transmitted through an abutment member 158 to the button 152 to operate the valve. A compression spring 159 resists the expansion of the pile of discs 154.

The operation of the form illustrated in Figure 14 is of the on-01f" type, that is, there is no modulation of the gas supply to the main burner, but the same is turned on and off as the temperature requirements rise and fall.

While the forms of the invention shown and described herein are fully capable of achieving the objects and providing the advantages hereinbefore stated, it will be realized by those skilled in the art that they are capable of some change without departure from the spirit of the invention. For this reason, I do not mean to be limited to the forms shown and described, but rather to the scope of the appended claims.

I claim:

1. In combination in a gas burning appliance of the "type having a main burner and a pilot burner: a main valve connected between a source of gas under pressure and said main burner; fluid motor means connected to said valve to close the same in response to fluid pressure delivered to said motor means; a three-way pilot safety valve connected between a source of gas under pressure and said pilot burner; conduit means interconnected between said safety valve and motor means; a first thermoresponsive control element connected to actuate said safety valve and positioned in heat transfer relation with said pilot burner to interrupt delivery of pilot gas to said pilot burner upon failure thereof and divert said pilot gas to said motor means to close said main valve; a second thermo-responsive control element connected to actuate said main valve to modulate the flow therethrough; and actuating means interposed in the path of movement of said second thermo-responsive control element and connected to said fluid motor means to actuate the latter to close said main valve at a predetermined point in the movement of said second control element.

2. The construction of claim 1 further characterized in that said last-named actuating means comprises a relay valve fluid-connected between said source of fluid under pressure and said motor means and having a movable member positioned in said path of movement.

3. A safety valve assembly for gas burning appliances of the type having a main burner, a pilot burner, a main valve, and a fluid motor to operate said main valve, said assembly comprising in combination: an air-intake means in said pilot burner communicating with said main burner; a first and a second three-way valve, each valve having an inlet passage, a pair of alternate exhaust passages, and a movable element to close one or the other of said exhaust passages selectively, one of said exhaust passages in each valve being communicated with the other; conduit connection means to communicate the inlet passage in said first valve to a source of gas under pressure, the other inlet passage to said fluid motor, the second remaining exhaust passage in said first valve to said pilot burner, and the second remaining exhaust passage in said second valve to a point in said air intake of said pilot burner; and thermo-sensitive means adapted to respond to the flame of said pilot burner to move said elements in unison to close said first exhaust passages when said pilot burner is lit whereby to deliver fuel gas through said first valve to said pilot burner and actuating gas through said'second valve from said motor to said burner, said thermo-sensitive means being adapted and connected to move said elements in unison to close said second exhaust passage when said pilot is extinguished whereby to deliver said gas under pressure through both of said valves to said motor.

4. The construction of claim 3 further characterized in that said thermo-sensitive means includes a thermoexpansive member positioned in the flame of said pilot burner and mechanically connected to apply force to move both of said movable elements when expanded and spring means to move said movable elements to close said second exhaust passages when said thermo-expansive element contracts.

5. The construction of claim 3 further characterized by having a manually operable thrust member to move the movable element in said first valve independently of said second valve whereby to open said first valve to deliver pilot gas to said burner to light the same.

6. A control system for gas burning appliances of the type having a main burner and a pilot burner, said control system comprising in combination: a main valve adapted to be connected between a source of gas under pressure and said main burner; a fluid motor in said main valve to close the same upon delivery of gas under pressure to amaze 11 said motor; a main conduit connectedbetween said;main valve and main burner to deliver gas to. thelatter; a pilot conduit connected between said main valve and pilot burnerto deliver gas to thevlatter; an ain supply in said pilot burner communicating with saidburner; a

bleed conduit connected to said pilot burner todischarge actuating gas from said motor intothe air-supply: ofi said pilot burner for consumption therein; a: safety valve adapted: for connectionbetween a source of? gas under pressure and said pilot burner, said safety valve being;

interposed in said bleed conduit and having a pilot flame responsive element to divert pilot burner supply gas throughsaid bleed conduit to close said main valve upon failure of saidipilotburner; and a three-way relay valve adapted for connection to said source offluid under pressure, to said fluid motor, and to said bleed conduit, said relay valve having a thermostatically actuated element movable toselectively admit gas under pressure to said fluid; motor or to discharge gas from said motor intosaid bleed conduit.

7. The construction of claim6further characterizedby having a thermostatically movable member connected. to said main valve to modulate the flow of gas. therethrough over a predetermined range, said last-named member being adapted; to engage said relay. valve to. closevsairl main valve upon reaching a lower limit of said range,

llafnmneea Cit d n h file ofithie patent UNITED STATES PATENTS 1,760,199 Janssen May 27, 1 930, ,8 0,5 Tuck, e g- 59, 1,853,196 Bogle Apr. 12, 1932 1,976,930 Evans Opt, 16, 193 41 1,999,731 Leins Apr 30, 1935 2,045,088 Kuenhold June 23 1936 2,192,630 Beam Man. 5, 1940 2,207,978 Gauger July 16, 1940 2,245,773 Grant "June 17, 1941 2,253,866 Quoos Aug, 26, 1941 2,328,279 Jones Aug. 31, 1943, 2,349,484 Converse May 23,1944 2,390,993 De Giers Dec, 18, 1945" 2,488,388 Evans Nov. 15, 1.949 2,504,964 Cunningham Apr. 25; 1,950 2,576,246 Taylor Nov. 27; 1951 2,599,457 Jones June 3, 1 952; 2,630,273 Susserott Mag. 3,1953 

